Quality of epitaxial InAs nanowires controlled by catalyst size in molecular beam epitaxy

Abstract

In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.

Quality Control of GaAs Nanowire Structures by Limiting As Flux in Molecular Beam Epitaxy

“…As can be seen, a clear tendency, as arrowed, is shown as the thinner the nanowire, the higher the Ga concentration in the catalyst during nanowire growth, which is consistent with previous studies. 36,40 Interestingly, this tendency is seen to be more remarkably for the high V/III ratio (as illustrated by the pink arrow in Figure 3e), possibly owing to the strong competition of Ga in catalysts caused by its lower partial pressure in the growth chamber. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 To understand our observations, two questions need to be answered.…”

“…34 It should be noted that the lateral dimensions of grown nanowires vary and the observed variations fit well with the size distribution estimated from the plan-view SEM images. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 It has been well documented that the catalyst composition and status are critical to the growth of III-V nanowires, 35,36 so that it is necessary to determine Ga concentration in the catalysts during the nanowire growth. Accordingly, EDS analysis was performed statistically on nanowire catalysts with different lateral dimensions in both samples.…”

Direct realizing the growth direction of epitaxial nanowires by electron microscopy

“…To solve this issue, the epitaxial nanowire growth provides the uniqueness that well aligned nanowires can be grown on the chosen substrates, and by selecting substrates with particular orientations, specifically orientated nanowires can be grown. The epitaxial III -V semiconductor nanowires are generally grown in metal-organic chemical vapor deposition [8][9][10], molecular beam epitaxy [11][12][13], chemical vapor deposition [14,15], through the vapor-liquid-solid [16][17][18][19] or the vapor-solid-solid mechanisms [20][21][22].…”

Polarity driven simultaneous growth of free-standing and lateral GaAsP epitaxial nanowires on GaAs (001) substrate

“…Figure 1(b) is such a sideview SEM image and shows that the angle between the growth direction of majority free-standing nanowires and the GaAs (001) substrate is 37. 5 , which corresponds to an angle between a h110i and a h111i directions, suggesting that the free-standing nanowires are along the h111i directions. Since there are two orthogonal h110i directions and 4 possible inclined h111i directions on the GaAs (001) substrate, it is necessary to understand why free-standing nanowires grew along only two h111i directions and why these nanowires are projected only along one h110i direction.…”

“…III-V epitaxial semiconductor nanowires have great potentials for applications in nanoelectronics and optoelectronics due to their direct band gap and thus high luminescence efficiency. [1][2][3] In general, III-V epitaxial nanowires can be grown on III-V substrates via the vapor-liquid-solid (VLS) mechanism 4 by dedicated growth techniques, such as molecular beam epitaxy 5 or metal-organic chemical vapour deposition (MOCVD). 6,7 In a typical nanowire growth using Au as the catalysts, Au nanoparticles form liquid droplets by alloying with group III element(s) at relatively low temperatures and in turn catalyze the free-standing epitaxial nanowires.…”